The present invention relates generally to plural-component spray systems. In particular, the present invention relates to reciprocating fluid proportioners having at least two pumps.
Fluid proportioners comprise dispensing systems that receive separate inert fluid components, mix the components in a predetermined ratio and then dispense the components as an activated compound. For example, fluid proportioners are used to dispense epoxies and polyurethanes that solidify after mixing of a resin component and an activating material, which are individually inert. However, after mixing an immediate chemical reaction begins taking place that results in the cross-linking, curing, and solidification of the mixture. Therefore, the two components are routed separately into the proportioner so that they can remain segregated as long as possible. A manifold receives each component after it is pumped separately and mixes the components so the mixture can be dispensed from a sprayer coupled to the manifold.
A typical fluid proportioner comprises a pair of positive displacement pumps that individually draw in fluid from separate fluid hoppers and pump pressurized fluids to the mix manifold. The pumps are driven in synchronicity by a common motor, typically an air motor or hydraulic motor, having a reciprocating drive shaft. Such configurations are simple and easy to design when the fluid components are dispensed in a 1:1 ratio and the pumps are of equal volumetric displacement. Force balancing in these configurations can be adequately accommodated by placing the motor halfway between the pumps. As such, forces generated between the pumps and the motor are equal.
Most two component epoxies and polyurethanes are not, however, comprised of a 1:1 ratio of the components. Typically a first major component is needed in a higher concentration than a second minor component. In such a case, displacement of one pump is required to be larger than the other. However, such systems can not be designed by simply placing the motor halfway between the pumps. Forces needed to drive each pump are different such that center mounting of the motor results in side loading that produces undesirable binding, wear and leakage.
Conventional fluid proportioners have used three pumps to deliver two components. For example, two pumps of equal displacement are used. Each will dispense half of the required volume of the major component. The motor is positioned halfway between these pumps. A third pump is used to dispense the minor component at the requisite volume. The third pump is placed in-line with the air motor. Thus, forces from the three pumps are balanced on all sides of the air motor.
Needless to say, conventional dual component fluid proportioners require the use of additional components, thereby increasing the weight, size and cost of the system. An additional pump, pressure gauge, manifold and hoses are needed to integrate the third pump with the two component system. For example, a splitter manifold is needed to separate fluid from the fluid source to the inlets of the two pumps providing the same fluid. Additionally, a mix manifold is needed to integrate fluid from the outlets of the two pumps providing the same fluid. The additional components increase the complexity of the system, reducing ease of operation. Furthermore, due to the increasing viscosities of compounds being developed, it has been necessary to increase the size of the motor used to pump the fluid components. This makes the driving of additional pumps even less desirable. There is therefore a need for improved multi-component proportioner systems.